M35A2 low oil pressure.....

[bart6453]

So my oil pressure has always been on the low side, and I noticed it seemed to be getting lower.

At idle it drops to pretty much zero..especially when hot. This never bothered me much, as I am a Harley guy and it is very, very normal for a H-D to show zero oil pressure at idle when warmed up.

Anyways.....I read on here that it was a bad thing, so I replaced the pressure sending unit just to make sure it was not that...and of course it is still reading low. I checked the connections on my gauge and they all seem pretty darn good.

What's the next step? Oil pressure regulator? if so...where and how do I clean/adjust it?

Or am I simply screwed and have worn out conrod bearings?

thanks in advance,

Bart

 

[stumps]

Check for oil dilution. The Fuel Density Compensator (If it is still plumbed in), the Injector Pump Hydraulic Head, and the Injector pump's fuel pump are popular places for diesel to get pumped directly into the oil sump.

-Chuck

 

[timntrucks]

my duece also shows a low pressure. i think mine is the gauge.. runs super fine for 2 years now

 

[G-Force]

Check it with a mechanical gauge.

 

[jatonka]

Go buy a mechanical gauge at auto zone or parts America or anywhere and put it where the sending unit goes, than you will know if you have low oil pressure. Then, get a manual on the repair/adjustment of the external oil pressure regulator over on the alternator side of the engine, behind the turbo sort of. It can be shimmed to increase oil pressure. You really ought to have around 30 psi or more at high rps and at least 15 psi or more at idle. JT out

 

[bart6453]

thanks for the quick reply...should I just get an oil test kit and send it off then? We do it once in a while for the old H-D's when we think there are issues.

I did pull an oil filter and the viscosity seemed about what it was when I put it in...of course this was all just by the old whiskey eye.

I suppose it would tell me if I have metal in the oil from the Conrods too....

 

[Kohburn]

since i bought mine it reads 30 running and then drops to ~0 at idle warmed up. I assumed that it was a mismatch between the gauge and the sender (60 psi gauge and maybe a 120psi sender)

 

[ZRacer]

I have the opposite problem. Once my Deuce gets started, oil pressure jumps to about 60 lbs. When it is running, it practically pegs the gauge at almost 120 psi. Even when warm and at idle, it reads 45 psi. Is this too high?

 

[stumps]

since i bought mine it reads 30 running and then drops to ~0 at idle warmed up. I assumed that it was a mismatch between the gauge and the sender (60 psi gauge and maybe a 120psi sender)

The only thing using a mismatched gauge and sender will do is give a proportionately wrong reading. It won't make the pressure drop as the truck warms up. That generally is a problem with the oil... or it can mean excessive bearing clearances.

If I was seeing pressures that I just couldn't believe, I would temporarily hook up a mechanical gauge as a check.

-Chuck

 

[blisters13]

Nuthin' like a old-fashioned gauge.....

 

[dittle]

I have the opposite problem. Once my Deuce gets started, oil pressure jumps to about 60 lbs. When it is running, it practically pegs the gauge at almost 120 psi. Even when warm and at idle, it reads 45 psi. Is this too high?

I had the same gauge combination in my truck. Nothing wrong with the truck, just the readout of the gauge is wrong. If you want to have correct readings just get a 0 - 60 gauge off ebay or somewhere.

 

[kurtkds]

The only thing using a mismatched gauge and sender will do is give a proportionately wrong reading. It won't make the pressure drop as the truck warms up. That generally is a problem with the oil... or it can mean excessive bearing clearances.

If I was seeing pressures that I just couldn't believe, I would temporarily hook up a mechanical gauge as a check.

-Chuck

When I got my deuce, the pressure gauge would read 30 PSI at idle, once up to temp idle pressure would be 0-5.

I found that I had a 120 PSI sending unit going to a 60 PSI Gauge, I changed the sending unit to a 60 PSI sender. I now have 50+ PSI at cold idle and 30 PSI at temp.

 

[Kohburn]

I have the opposite problem. Once my Deuce gets started, oil pressure jumps to about 60 lbs. When it is running, it practically pegs the gauge at almost 120 psi. Even when warm and at idle, it reads 45 psi. Is this too high?

sounds like we need to swap gauges

 

[Kohburn]

That generally is a problem with the oil... or it can mean excessive bearing clearances.

I've never had a vehicle that the oil pressure at idle didn't drop once warmed up. It's a simple matter of fluid viscocity thinning with heat.

 

[bart6453]

So....out of curiosity, if my engine had too much clearance in the rod bearings...wouldnt I hear her knocking around a bit?

 

[RANDYDIRT]

Don't they all knock? Seriously though... If it were a cam bearing or a main you may never hear a thing. As loud as these engines are, you may not hear a rod until it's about to grenade.

Dirt

 

[blisters13]

When I got my deuce, the pressure gauge would read 30 PSI at idle, once up to temp idle pressure would be 0-5.

I found that I had a 120 PSI sending unit going to a 60 PSI Gauge, I changed the sending unit to a 60 PSI sender. I now have 50+ PSI at cold idle and 30 PSI at temp.

Probably why the truck got de-acquisitioned. Someone did a bad repair and then someone else said, "That engine ain't no good; get rid of it."

 

[jollyroger]

My deuce reads 60 psi ALL the time on a 60 psi guage unless it is real cold out and the engine is idling low. Then it reads 50 psi till it warms up and the idle speed increases. I don't know what the actual top end pressure is.

 

[coyotegray]

Probably why the truck got de-acquisitioned. Someone did a bad repair and then someone else said, "That engine ain't no good; get rid of it."

I like it when that happens!!

 

[stumps]

My truck reads a solid 30-40 psi at idle on a 120psi gauge, and 60-80 when at highway speeds.

-Chuck